This concerns a decorative sheet material of sufficient thickness and durability that it is suitable for use as a floor covering. More particularly, it concerns a multilayered sheet material in which a colored design extends through the thickness of a major layer of the sheet material. Advantageously, the colored design is formed by a vinyl chloride plastisol. This also concerns a method for making such sheet material in a continuous process.
The vinyl sheet flooring manufactured today is primarily cushion sheet vinyl flooring and inlaid vinyl flooring. Of the two, inlaid vinyl sheet is the more desirable and commands the higher price because the decorative layer extends through the thickness of most of the sheet. To form an inlaid vinyl sheet, different colored vinyl chips are deposited on a stationary base layer in the desired decorative pattern. A clear urethane wear layer may be applied over this pattern which is then embossed in register with the desired decorative design. For example, to form an inlaid vinyl sheet having a pattern of multicolored bricks, predominately dark red chips might be deposited from a first stencil to form a first pattern representative of dark red bricks; somewhat lighter red chips might be deposited from a second stencil to form a second pattern in register with the first that is representative of lighter colored bricks; still lighter red chips might be deposited from a third stencil to form a third pattern in register with the other two; and predominately gray vinyl chips might be deposited to form a fourth pattern in register with the other three that is representative of the mortar between said bricks. Even more colors and stencils may be used as desired.
The resulting floor covering is highly desirable commercially since the color of the pattern extends throughout the thickness of the layer deposited atop the base layer. Typically, this layer is 35 mils or more thick and is considerably thicker than a urethane wear layer which ordinarily is about 2.50 mils thick. As a result, even if heavy usage should remove the wear layer, the flooring still retains its color until the entire thickness of the decorative layer is worn through. As will be apparent, however, the conventional manufacture of inlaid sheeting as described above is a complicated intermittent process that adds considerably to the expense of the vinyl product.
The apparatus for making conventional inlaid vinyl sheeting includes a conveyor belt on which the base layer is transported, a series of stencils which deposit the different colored vinyl chips on the base layer in the desired decorative pattern, a coater for applying a clear urethane wear layer, an oven for fusing the vinyl chips and wear layer and an embosser to emboss the pattern design. To make the inlaid sheets, the colored vinyl chips are manufactured by mixing vinyl resin, plasticizer, filler and pigment, forming sheets of the resulting mix, and then grinding up the sheets to form vinyl chips. The chips are then screened so that that are all within the desired size range. Next, the chips are placed in hoppers above the appropriate stencils. The base layer, which illustratively is an asbestos sheet, is then transported past the stencils. When the base layer is properly aligned with each stencil, it is stopped and the vinyl chips are raked across the stencil so that they fall through holes in the stencil to create a pattern on the base layer. The holes in the different stencils are aligned with one another so that the colored chips from the different stencils form a composite pattern on the base layer.
As will be apparent, the use of vinyl chips to make colored designs creates substantial color control and inventory problems at any high-speed, high-volume production facility. To ensure that each color is substantially uniform throughout a production run, it is necessary to prepare in advance of the production run all the vinyl chips that are used in that run. This requires the use of substantial storage capacity and all manner of equipment to transport the chips from storage bins to the stencils. Production is further complicated by the need to minimize downtime while refilling the supply of chips at the stencils.
Since the vinyl chips are resilient solids they tend to scatter in random directions at the time they are deposited on the base layer. This leads to a certain intermixing of the colors of the different patterns deposited on the base layer, a feature which may find attractive. In order to enhance this effect and provide some control over the amount of color intermixing that occurs, it is often desirable to intentionally intermix small amounts of vinyl chips of one or more colors with vinyl chips of another color. This, however, greatly increases the inventory of colors and the storage problems attendant thereto.
The scattering of vinyl chips also makes it impossible to define a pattern with precision. Adjacent patterns tend to blend into one another and it is difficult to determine where one begins or the other ends. While these effects are often attractive, they present limitations on the designs that can be used with inlaid vinyl flooring. In addition, this chip blending effect makes it difficult to obtain a distinct embossing in register with the pattern since the outline of the pattern is often vague. The scattering of the chips also affects the repeatability of a pattern because the same element in a pattern may not begin at the same spacing from adjacent elements in every replication of the pattern. Obviously, this can be a problem where it is necessary to match a pattern along the edges of two sheets.